DESCRIPTION: The investigators propose to test the feasibility of developing a radiopharmaceutical based on Tc-99m-labeled vasoactive intestinal peptide for receptor-specific uptake on tumors with over-expression, as further described by their abstract: "Each year more than 165,000 new cases of colorectal cancer are diagnosed in the USA. It is the third cause of cancer-related deaths in the country. A survey of the literature leads to the conclusion that the need exists to develop Tc-99m labeled receptor specific agents for early diagnosis of colorectal cancers and their metastatic lesions. Early detection will prompt for surgical and/or aggressive therapeutic interventions and may minimize morbidity and mortality. "Evidence is abundant in the literature that vasoactive intestinal peptide (VIP) receptors are expressed in high density on colorectal cancer cells and that the tumors and their metastatic lesions can be efficiently imaged with I-123-VIP. "We have prepared VIP analog TP 3654 and labeled it with Tc-99m by an instant kit procedure. The yields are quantitative, the agent is stable and its biological activity is not comprised. Results in mice bearing human colorectal cancer LS174T also indicate that the tumor uptake was receptor specific and that tumors were delineated by scintigraphic imaging. Our specific aims are: 1) to enhance tumor uptake by using high specific activity preparations, 2) to minimize renal uptake by pre- or co-injecting lysine, 3) to compare the efficacy of Tc-99m TP 3654 with recently approved TC-99m-anti-CEA scan and In-111-DTPA-(D)-Phe-Octreotide and 4) to determine receptor specificity of the agent for other human colorectal cell lines in vitro. Together, we will learn more about how cell surface receptors can be utilized for early detection of cancer and lead us to develop Tc-99m labeled VIP analog TP 3654 as an agent for imaging colorectal cancer." PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE